1. Field of the Invention
The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program such as a wireless LAN (Local Area Network) for communicating between a plurality of wireless stations. In particular, the present invention concerns a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program for managing a network in such a manner that at least part of the communication stations notify a beacon in which information about the network is described.
Further, more specifically, the present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program for allowing a communication station to perform data communication in which a band is guaranteed with a band reservation scheme. In particular, the present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program for mediating a conflict over a reservation band between communication stations with low-load processing and avoiding the conflict of reservation use.
2. Description of the Related Art
Computer networking including a LAN can efficiently realize the sharing of information resources and the sharing of equipment resources. Nowadays, attention is being given to a wireless LAN as a system that frees users from cabling of conventional wired LANs. The wireless LAN can eliminate most of cables from workspaces such as offices. Accordingly, it is possible to relatively easily move communication terminals such as personal computers (PCs).
In recent years, there is remarkably increasing demand for wireless LAN systems as they achieve higher speeds and become available at reduced costs. Particularly, introduction of a personal area network (PAN) is being considered to construct small-scale networks for information communication between electronic devices available around users. For example, some different wireless communication systems and wireless communication apparatuses have been standardized by utilizing such frequency bands as 2.4 GHz and 5 GHz which require no license from an administrative government office.
Canonical standards concerning wireless networks can include IEEE (The Institute of Electrical and Electronics Engineers) 802.11 (e.g., see non-patent document 1), HiperLAN/2 (e.g., see non-patent document 2 or 3), IEEE802.15.3, and Bluetooth communication, for example. The IEEE802.11 has enhanced standards such as IEEE802.11a (e.g., see non-patent document 4), b, and g depending on differences of wireless communication systems and frequency bands.
Further, a so-called “ultra-wideband (UWB) communication” for carrying out the wireless communications by putting information on very weak impulse series is attracting attention as a short range, ultra-high speed wireless communication system, and this system is expected to be made practicable. An access control system of ultra-wideband (UWB) communication is now under review in IEEE802.15.3 and the like.
According to a general method of constructing a local area network using the wireless technology, there is provided one apparatus called an “access point” or a“coordinator” functioning as a control station inside the area. The network is formed under overall control of the control station. For this kind of wireless network there is broadly used an access control method based on the band reservation, in which communication apparatuses synchronize with each other through the mediation of the access point. In other words, when a given communication apparatus transmits information, a band needed for the information transmission is firstly reserved through the access point so that the communication apparatus can use a transmission path without conflict with information transmission by another communication apparatus.
On the other hand, there arises a problem to significantly decrease efficiency of using the transmission path in the case of performing asynchronous communication between transmitting and receiving communication apparatuses in the wireless communication system having the access point because it is absolutely necessary to perform wireless communication through the access point. For this reason, as another method of constructing a wireless network, there is proposed a so-called “ad-hoc communication” for directly performing asynchronous communication between communication stations operating autonomously. Particularly, in a small-scale wireless network composed of a relatively small number of clients that locate close to each other, it is considered that such ad-hoc communication is suitable because any terminal can directly perform asynchronous wireless communication without using a particular access point.
An ad-hoc wireless communication system has no central control station. Accordingly, this system is suited for constructing a home network composed of household electric appliances. The ad-hoc network has several features. For example, if one apparatus fails or is powered off, the routing is automatically changed, making the network strong against crash. Since a packet is hopped more than once between mobile stations, data can be transferred to a relatively distant destination with a high data rate maintained. There are known various development examples about the ad-hoc system (e.g., see non-patent document 5).
In the case of transmitting real-time, namely, consecutive data such as AV contents which need to be sent at evenly spaced time intervals, it is necessary to guarantee the band.
In conventional band reservation communication, the above-mentioned wireless communication system managed under the control of the control station is typically employed, and the control station reserves a band in response to a band use request from each terminal station.
For example, according to the standard of a wireless personal area network (WPAN) in IEEE 802.15.3, there is defined time-division multiplexing in which a control station called a coordinator assigns a necessary communication band as a guaranteed time slot (GTS) in response to a request from a communication apparatus as a terminal station. In this case, the control station can perform the centralized management of bands to be used, so that a communication apparatus as a terminal can transmit without conflict with transmission by another communication apparatus. Further, there is proposed a method that, in the case where a conflict over a use band occurs between communication apparatuses belonging to different networks, communication apparatuses that have detected the conflict report the situation to their respective control stations, which then assign different bands to the communication apparatuses.
[Non-patent document 1] International Standard ISO/IEC 8802-11:1999(E) ANSI/IEEE Std 802.11, 1999 Edition, Part11:Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications
[Non-patent document 2] ETSI Standard ETSI TS 101 761-1 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part1: Basic Data Transport Functions
[Non-patent document 3] ETSI TS 101 761-2 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part2: Radio Link Control (RLC) sublayer
[Non-patent document 4] Supplement to IEEE Standard for Information technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements-Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHZ Band
[Non-patent document 5] C. K. Tho, “Ad Hoc Mobile Wireless Network” (Prentice Hall PTR)